Professor’s Diary: Fukushima radioactive material “has reached the west coast as of June 2013 by ocean transport” — Health risks to be determined by ongoing monitoring

Jay T. Cullen, Associate Professor of marine chemistry at the University of Victoria, Daily Kos diary, Jan. 4, 2014: […] Fukushima derived Cs has reached the west coast as of June 2013 by ocean transport but [the] concentrations of Cs continue to be well below levels thought to pose environmental or public health threats. There have been a number of popular press articles that […] report the timing of the arrival of the radionuclides but offer no perspective on the actual levels and the associated risk to residents of the west coast (e.g. link). […] About 93% of radioactivity in seawater results from the presence of primordial, naturally occurring potassium-40 (K-40) and rubidium-87 (Rb-87). The remaining 7% are radioactive elements deposited to the ocean from past atmospheric nuclear testing. […] Fukushima derived Cs was detected all the way to the coast in June 2013 with the highest levels of Cs-137 farthest offshore (0.0009 Bq/L or roughly 0.006% of background radiation) and lower levels of 0.0003 Bq/L toward the coast […] Ongoing monitoring will constrain the likely environmental and health risks posed by ocean transport of Fukushima derived radionuclides.

Note the professor changed the units to Bq/L for Cs-134 and -137, instead of using Bq/m3 as in the source document. The above amounts must be multiplied by 1,000 to get Bq/m3.

In addition, the figures provided by the professor appear to be inaccurate:

According to the source document, it’s Cs-134, not Cs-137, that measured 0.9 Bq/m3 (or 0.0009 Bq/L if you modify the units like the professor)..
The professor writes that in June 2013 there were “lower levels of 0.0003 Bq/L toward the coast” — This amount is not in the measurements for 2013, the only mention of it was in 2012: “Levels of 137Cs equal to 0.3 Bq/m3 measured at Sta. P26 in 2012.”
Last month in a Vancouver-area newspaper Prof. Cullen wrote: “the natural level of radioactivity on average in the oceans is about 13 Bq/L, against which radioactivity resulting from human activities and disasters should always be discussed.” What is the basis of this claim that “natural radioactivity levels should always be discussed” when “radioactivity resulting from human activities” is mentioned?

“In the ocean (and human body) different radionuclides have different fate and toxicity,” according to Woods Hole Oceanographic Institution’s senior scientist Ken Buesseler (who mentions his ability to be quoted in media reports downplaying Fukushima-related data).

Also be aware that fish can bio-concentrate cesium-137 at a rate of 100 times the level found in the surrounding water. For seals and sea lions it’s up to 1,000 times. (Source: IAEA)